1. Field of the Invention
This invention generally relates to methods of ink printing and, more particularly, to multicolor ink printing on paper and paper-like substrates. This invention also relates to systems and apparatuses for multicolor ink jet printing on papers, as well as multicolor ink printed papers, per se.
2. Description of the Prior Art
As defined herein, the term xe2x80x9ccolor spacexe2x80x9d is a mathematical definition for colors. Well known color spaces include CIE lab, CIE xyz, CIE luv, CIE xyY, CIE uvY, Cyan-Magenta-Yellow-Black (CMYK), and Red-Green-Blue (RGB). For example, the RGB triplet divides each color into its red, green, and blue components and expresses those components as a value between 0 (minimum) and 255 (maximum), such as (50, 40, 220) for a blue-dominant color. Each component of the RGB triplet may also be expressed as the quotient of the given value divided by the maximum value, such as (0.196, 0.157, 0.863) for the blue-dominant color previously defined as (50, 40, 220).
Overall changes in the printing and imaging industries compound the traditional problems, especially as digital technology becomes the norm rather than the exception. For example, digital images are routinely coded in RGB for display on a computer monitor. However, printers typically use CMYK, and textile colorists traditionally use CIE lab. Thus, an image initially in RGB will be routinely converted into a different color space before being printed. However, data can easily be lost or corrupted in the conversion to a different color space. Software correction may be applied in an attempt to recover lost or corrupted data, but such software correction may actually increase the errors.
Many prior art methods for printing attempt to overcome the disadvantages inherent in multiple color space transformations, such as U.S. Pat. No. 5,450,217 to Eschbach et al. and U.S. Pat. No. 5,953,499 to Narendranath et al. These patents rely on artificial blending or filtering color space data to xe2x80x9cenhancexe2x80x9d or xe2x80x9cimprovexe2x80x9d the subsequently rendered image. Yet, clearly, such forced techniques are not ideal.
Improvements in hardware and software make it possible to use more than three dyes to make a color. However, current systems and method usually do not fully utilize these improvements. For example, gray scales are usually made with a dithered black, a dithered gray, or a combination of both dithered black and gray. Yet, dithered blacks and grays generally do not reproduce deep and true blacks and grays. It has been found that, by using multiple overlapping sets of complementary colors, a composite shading scale can be built that provides a robust shading scale without visible dithering patterns and also allows for subtle casts to color renderings.
The ink jet printing art is generally directed to printing with sets of 4 to 8 differently colored inks. This direction of the art is discussed in U.S. Pat. No. 5,833,743 to Elwakil.
There is a need in the ink jet printing art for a system that provides both a broad range of shading and vivid, bright, and true colors, wherein complex digital images can be faithfully printed.
In light of the foregoing, it is an object of the present invention to provide a method for printing an image directly from a digital image with specific user-defined inks.
It is also an object of the present invention to provide such a method for printing an image, wherein the user selects 8 to 16 inks to create a user-defined high-multiplicity ink set. The user-defined ink-set is linearized with user-defined calibration curves.
It is a further object of the present invention to provide such a method for printing an image, wherein the pixels of the digital image are directly correlated with the ink set using hue and shade values, without transformation into conventional color spaces, such as CIE lab, CIE xyz, CIE luv, CIE xyY, CIE uvY, or CMYK.
In addition, it is an object of the present invention to provide a system for selecting inks for printing, in which a user-defined ink set profile is used to correlate an amount of inks with hue and shade values derived directly from the pixels of a digital image defined in the RGB color space.
Moreover, it is an object of the present invention to provide an apparatus for paper printing having a plurality of inks calibrated as a user-defined ink profile that prints an amount of selected inks on a paper based on hue and shade values from the pixels of a digital image.
Furthermore, it is an object of the present invention to provide a printed paper having a high dpi (dots per inch) count, and a broad range of color density and shading. It is a further object of the present invention to provide a printed paper or like printed substrate with different types of dyes (e.g., acid and fiber-reactive), and yet achieve faithful reproduction of complex pictorials and images.
These and other objects of the present invention are preferably achieved by a method of reproducing a digital image on a paper including the steps of the user selecting 8 to 16 inks to form an ink set, calibrating the ink set to create an ink set profile, using the ink set profile to calculate hue-based and/or shade-based look-up tables (LUTs) that directly correlate the inks with the color space coordinates (e.g., RGB values) of the pixels of the digital image. By directly correlating the inks and the color space coordinates using hue and shade, the present method faithfully reproduces the digital image. The method may be practiced using a system and/or apparatus that provides means for performing the calibration of the ink set and direct correlation of the color space coordinates. The printed substrate has a first plurality of dots having 8 to 16 differently colored inks per dot and a second plurality of dots having one color per dot. The 8 to 16 differently colored inks are user-defined and avoid certain conventional art directed ink jet ink-set colors, particularly including gray. Significantly, the method, system, and apparatus produce a printed paper having a high level of detail, depth of color, and broad range of shading. The printed paper substrate also has a combination of dye types that heretofore were considered incompatible. One preferred embodiment has 12 inks, which includes or provides 7 true colors, 4 pseudo-colors (i.e., a mix of two or more true colors), and black, and wherein 8 colors are fiber-reactive inks and 4 colors are acid inks.
In one preferred embodiment, the printable substrate is a fiber containing substrate, and most preferably a high cotton content paper.